Depends on whether or not the person who had it before you redeemed the offer or not many people have bought it and have gotten the 100GB including myself...its just the luck of this.
If no one has claimed the 100GB storage, then you might be able to use it. The help page says it is not available to used or refurbished units, but a power wash might fix that.
Models aren't eligible either but I was able to claim it for mine. always better to ask for forgiveness than to ask for permission (if you want to get anything done in this bought a refurbished unit 3 weeks on eBay and I was lucky enough, I had no problems getting my 100GB from Google Drive. I saw the note that it does not apply, but I got it anyway! Was 129$ on Nextbuying http://www.nextbuying.com/ .
I tried to activate the 100 GB Drive space through the CB itself it failed, 100 GB google drive don't apply to refurbished Chromebook.
Picking up a Acer C7 through their outlet on ebay, but it doesn't say anything about the 100 GB Drive storage. Does anyone know if units include the Drive storage